Wireless communication may be used as a means of accessing a network. Wireless communication has certain advantages over wired communications for accessing a network. One of those advantages is a lower cost of infrastructure to provide access to many separate locations or addresses compared to wired communications. This is the so-called “last mile” problem. Another advantage is mobility. Wireless communication devices, such as cell phones, are not tied by wires to a fixed location. To use wireless communication to access a network, a customer needs to have at least one transceiver in active communication with another transceiver that is connected to the network.
To facilitate wireless communications, the Institute of Electrical and Electronics Engineers (IEEE) has promulgated a number of wireless standards. These include the 802.11 (WiFi) standards and the 802.16 (WiMAX) standards. Likewise, the International Telecommunication Union (ITU) has promulgated standards to facilitate wireless communications. This includes TIA-856, which is also known as Evolution-Data Optimized (EV-DO). The European Telecommunications Standards Institute (ETSI) has also promulgated a standard known as long term evolution (LTE). Additional standards such as the fourth generation communication system (4G) are also being pursued. These standards pursue the aim of providing a comprehensive IP solution where voice, data, and streamed multimedia can be given to users on an “anytime, anywhere” basis. These standards also aim to provide higher data rates than previous generations. All of these standards may include specifications for various aspects of wireless communication with a network. These aspects include processes for registering on the network, carrier modulation, frequency bands of operation, and message formats.
To aid in channel estimation, cell selection, and handover, these standards may specify that reference signals (a.k.a., pilot signals) are broadcast. According to some estimates, these reference signals may occupy, as non-data carrying overhead, as much as 20% of the available channel bandwidth.
Overview
In an embodiment, a method of operating a communication system includes allocating a first subframe of air interface resource elements and allocating a second subframe of air interface resource elements. The first subframe comprises a first plurality of air interface resource elements. The first plurality of air interface resource elements include a first plurality of reference signal resource elements and a first plurality data signal resource elements. The second subframe comprises a second plurality of air interface resource elements. The second plurality of air interface resource elements include a second plurality of reference signal resource elements and a second plurality data signal resource elements. The second plurality of data signal resource elements corresponding in time and frequency to the first plurality of data signal resource elements. Using a multi-antenna mode, the first subframe is simultaneously transmitted from a first antenna while the second subframe is transmitted from a second antenna. The first subframe is transmitted after applying a first orthogonal code of a family of orthogonal codes to said first subframe. The second subframe is transmitted after applying a second orthogonal code of the family of orthogonal codes to said second subframe.
In an embodiment, a communication system includes a wireless station that communicates using a multi-antenna air interface. The wireless station simultaneously transmits a first subframe from a first antenna and a second subframe from a second antenna. The first subframe has a first plurality of reference signal air interface elements and a first plurality of data signal air interface elements. The second subframe has a second plurality of reference signal air interface elements and a second plurality of data signal air interface elements. The first plurality of reference signal air interface elements are encoded with a first orthogonal code of a family of orthogonal codes and the second plurality of data signal air interface elements encoded with a second orthogonal code of the family of orthogonal codes. An air interface resource allocation system places the second plurality of data signal air interface elements in time and frequency locations in the second subframe that correspond to time and frequency locations of the first plurality of reference signal air interface elements in the first subframe.
In an embodiment, a method of operating a communication system includes allocating a first subframe of air interface resource elements. The first subframe includes a first plurality of air interface resource elements. The first plurality of air interface resource elements includes a first plurality of reference signal resource elements and a first plurality data signal resource elements. A second subframe of air interface resource elements is also allocated. The second subframe includes a second plurality of air interface resource elements. The second plurality of air interface resource elements includes a second plurality of reference signal resource elements and a second plurality data signal resource elements. The second plurality of reference signal resource elements correspond in time and frequency to the first plurality of reference signal resource elements. Using a multi-antenna mode, the first subframe is transmitted from a first antenna simultaneously with the second subframe's transmission from a second antenna. The first subframe is transmitted after a first orthogonal code of a family of orthogonal codes is applied to the first plurality of reference signal resource elements. The second subframe is transmitted after a second orthogonal code of the family of orthogonal codes is applied to the second plurality of reference signal resource elements.